We have the following setup:

PC with EW version 7 with 4 HDMI outputs

1 output for the EW operator

1 output front of house

1 output for foldback

1 output (alternate output) for subtitles in lower third

We mix our video for the live stream using an ATEM production studio. 

For the subtitles (songs and scriptures), we use a theme in the alternate output with a green background. The text is white with a black border.
In the ATEM we filter the green so we have a perfect subtitle on our streams. This works great.

However, if the EW operator clicks on "black", the alternate output becomes black as well. Can we prevent this? We would like the subtitles to disappear, but we do not want thealternate screen to become black. Also, videos and powerpoint should not appear on the alternate screen, we mix this by using the FOH output when we want it specifically.

Thanks for help!   

By the way, this issue would be solved if we could choose the color of the screen when you press "black".
So, if I press Black, I want the alternate screen to show completely green (or any other color that we shoukd be able to pick).
In the case, the subtitles would disappear, and any other content is not shown as well. Exactly what we want.

Have you considered using the CLEAR option instead of the BLACK. The clear just removes the text and leaves the background as it was. Maybe that will do what you want. Just a thought.

I'm not an EW Employee or Support person, just a user attempting to help other users.

If you aren't already using the Logo button you might want to create a image that suits you and set that as the Logo image that you could use for this. Just a thought.